Many vehicles, such as dump trucks, have a dump body with a tailgate pivotally attached at an upper end to the dump body in a tailgate opening. Depending upon the particular operation, the lower end of the tailgate may need to be either released from or secured against the vehicle body. A variety of different types of devices have been designed to be able to release and secure the lower end of a tailgate against the vehicle body, but each of these designs have problems.
For example, one type of prior apparatus includes a longitudinally extending hydraulic cylinder which is connected to a latching mechanism on each side of the vehicle body. When engaged, a piston in each of the hydraulic cylinders is either driven out or is pulled in along a longitudinal direction to pivot the latching mechanism connected to the hydraulic cylinder between a position releasing the lower end of the tailgate and a position securing the lower end of the tailgate against the vehicle body. Some examples of this type of device are set forth in U.S. Pat. No. 2,220,202 to Bohn, U.S. Pat. No. 3,811,729 to Vornberger, and U.S. Pat. No. 3,860,288 to Martin et al., which are all herein incorporated by reference. One of the problems with this apparatus is that a separate actuator is required to control the latching mechanism on each side of the vehicle body. This adds to the complexity and cost of the apparatus. This apparatus may experience problems in synchronizing the latching mechanisms on each side to release from or secure against the lower end of the tailgate against dump body at the same time because two actuators are used. As a result, one side of the lower end of the tailgate may not be released in time thus holding the tailgate in a secured position longer than desired or one side of the lower end of the tailgate may not be secured permitting materials in the dump body to seep out on that side. If the dump body only has one latching mechanism, then the tailgate will not be securely held against the vehicle body. Another problem with these devices is that the hydraulic cylinders used to operate the latching mechanism have high maintenance costs because the pistons are repeatedly exposed to contaminants, such as dirt.
Another similar apparatus also includes a longitudinally extending hydraulic cylinder which is connected to a latching mechanism on each side of the vehicle body. The apparatus also includes a latch position sensor on each side which monitors the state of the latching mechanisms, i.e. latched or unlatched, a hoist controller which can lower, hold and raise the vehicle body, and hoist lock which can prevent the hoist controller from raising the vehicle body. If the latch position sensors sense that the latching mechanisms are latched, then the hoist lock prevents the hoist controller from raising the dump body until the latching mechanisms are unlatched. One example of this type of device is set forth in U.S. Pat. No. 4,109,963 to Sieving et al. which are herein incorporated by reference. Again, one of the problems with this type of apparatus is that a separate actuator and a separate latch position sensor is required on each side of the vehicle body. This adds to the complexity and cost of this type of apparatus. If the dump body only has one latching mechanism, then the tailgate will not be securely held against the vehicle body. Another problem is that the hydraulic cylinders used to operate the latching mechanism have high maintenance costs because the pistons are repeatedly exposed to contaminants, such as dirt. Further, this apparatus requires a complicated and costly monitoring and locking system to prevent the dump body from being raised with the tailgate in a latched position.
Another apparatus incorporates a hydraulic cylinder on each side of the body which extends in the vertical direction with respect to the longitudinally extending truck frame and body. One end of each hydraulic cylinder is connected to a latching mechanism on each side of the dump body and the other end of each hydraulic cylinder is connected to the tailgate. When the hydraulic cylinder is engaged, each of the hydraulic cylinders is initially pushed in a downward direction which pivots the latching mechanisms to release and then stops. Meanwhile, a piston in the other end of the hydraulic cylinder continues to extend in a generally upward direction to raise the tailgate. Some examples of these types of devices are set forth in U.S. Pat. No. 3,860,288 to Norton et al. and U.S. Pat. No. 4,307,541 to Farmer et al. which are herein incorporated by reference. Again, one of the problems with this type of apparatus is that a separate actuator is required to control the latching mechanism or each side of the dump body. This adds to the complexity and cost of this type of apparatus. If the dump body only has one latching mechanism, then the tailgate will not be securely held against the vehicle body. Another problem is that the hydraulic cylinders used to operate the latching mechanism have high maintenance costs because the pistons are repeatedly exposed to contaminants.
Another apparatus includes a latch connected at one end of a lever arm which is connected to the upper end of a tailgate. A latch and lever arm are located on each side of the truck. A cable on each side is connected at one end to the latch on that side and at the other end to the truck frame. As the dump body is raised, the latches are disengaged by the cables and the lever arms are pivoted to raise the tailgate. One example of this type of device is set forth in U.S. Pat. No. 5,092,656 to Eldridge which is herein incorporated by reference. One of the problems with this apparatus is that the latches are located at the upper end of the tailgate. As a result, the lower end of the tailgate is not tightly secured and material may seep out of the dump body. Additionally, another problem is that a separate actuator is required to control the operation of the latches on each side of the dump body. This adds to the complexity and cost of this apparatus.